1. Field of Invention
The present invention relates to a prosthesis to surgically correct inguinal hernia and particularly to a prosthesis formed of two parallel layers of biocompatible net which are joined one to the other in a translational way.
2. Description of Related Art
It is known that the wall defects of the inguinal canal, which cause inguinal hernia, are surgically corrected by means of prostheses formed of profiled pieces of biocompatible material, normally net-shaped. Said known prostheses are generally formed of a net sheet, provided with a hole for the passage of the spermatic cord, which is applied by the surgeon on the suprafascial plane parallel to the back wall of the inguinal canal (according to the well known Liechtenstein technique). This kind of prosthesis imply the risk of relapses especially in the region of the internal inguinal orifice, due to the fact that the prosthesis is applied on a plane which is considerably distant, above said orifice. Another kind of known prosthesis consists in a so-called xe2x80x9cplugxe2x80x9d of biocompatible material which is inserted like a stopper in the internal inguinal orifice. Inserting said kind of prosthesis implies drawbacks due to the patient""s intolerance towards the material, because of the difficult incorporation of such a voluminous and tied up prosthesis.
Prostheses formed of many layers of biocompatible material have been recently proposed in the attempt to solve said drawbacks of the above described prostheses. EP-A-0719 527 describes a prosthesis for surgically correcting an inguinal hernia comprising an upper layer and a lower layer connected to each other by knitting. A hole is provided in said lower layer for the passage of the spermatic cord, and connected by means of a cut to an external edge of the same lower layer.
In WO96/14805 a prosthesis formed of two layers of biocompatible material which are applied one over the other on the same plane in the suprafascial region is described. Also this kind of prosthesis implies several drawbacks. The first drawback is that the plane of application of the prosthesis is above the fascia transversalis and therefore above the aponeurotic muscle, so that some of the drawbacks of the Liechtenstein method arise again. Further, this kind of prosthesis has another drawback, which is that the exit point of the cord from the prosthesis upper layer out of alignment with respect to the exit point of the cord of the underlying layer and therefore, since practically no space is provided between the two layers, the cord is pressed between the two layers of the prosthesis.
Further, a two layers prothesis has been recently marketed, which eliminates the first of the drawbacks of the prosthesis described in WO 96/14805 because one of the two layers is applied above the fascia transversalis and the other under said fascia, that is under the aponeurotic muscle plane. Consequently, the internal oblique and transverse muscles can keep exerting their xe2x80x9cshutterxe2x80x9d mechanism in a physiological way. However, even this recent kind of prosthesis is not free from drawbacks. For example, the central pin which connects the two layers represents an impediment for the above mentioned xe2x80x9cshutterxe2x80x9d mechanism. Further, said prosthesis does not provide for a suitable passage for the spermatic cord which, in order to come to the surface, is compelled to a route with a first curve and a second curve in the opposite direction and a consequent risk of xe2x80x9ckneeling downxe2x80x9d of the cord important structures.
Object of the present invention is therefore providing a prosthesis which is free from the above described drawbacks and particularly a prosthesis with two layers which can be respectively applied above and under the fascia transversalis, in the meantime providing an anatomically physiological passage for the spermatic cord. Said object is obtained according to the present invention with the prosthesis having the features specified in claim 1. Further features of the prosthesis according to the present invention are specified in the dependent claims from 2 to 5.
The two layers prosthesis according to the present invention offers the advantage that the spermatic cord, besides finding a physiologically correct passage between the two layers of the prosthesis, does not present any risk of xe2x80x9ckneeling downxe2x80x9d or squashing.
Another advantage of the prosthesis according to the present invention is that the two layers, although they are suitably spaced from each other since they are applied respectively above and under the fascia transversalis, are joined together by a band which allows axial translations of the upper layer in order to enable a better adjustment to the unavoidable, although small, anatomic variables of the distance between the external edge of the lower portion of the cord and the tuberculum pubicum, that is the bone whereto the inguinal ligaments are fixed.